This invention relates generally to medical devices used to monitor the electrical activity of living tissue. Specifically, this invention relates to an apparatus for atraumatically monitoring the electrical activity of living tissue during a medical procedure to provide information for ensuring that only certain tissue is affected by the procedure, and that surrounding tissue is not. This invention is particularly, though not exclusively, useful in surgical procedures, such as removal of tumors from the eighth cranial nerve without resulting in brain stem injury or interruption of the auditory pathways.